Author: Robert Hyatt
Date: 20:05:28 08/06/01
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On August 06, 2001 at 20:00:40, Pham Minh Tri wrote: >On August 06, 2001 at 00:16:54, Robert Hyatt wrote: > >>On August 05, 2001 at 10:25:46, Pham Minh Tri wrote: >> >>>Hi all, >>>Some my questions as I start my EGTBs: >>>1) What have I to do when there are more pieces than I need (for probing EGTB)? >>>For example, I have table of KBNK, but an endgame is KBNPK. Give the "redundant" >>>pieces for opponent? >> >> >>No. You only probe after a capture move, and only when the capture takes to >>you to a number of pieces you know you have tables for. IE if you only have >>3-4 piece tables, you only probe after a capture takes you to 4 or fewer >>pieces. >> >> >>>2) I see that index for EGTB is not simple, so why do we not apply the same >>>technique as opening book: use hashkey? I guess one of the reasons is to save >>>space for TBs - use halves of them. But I think we could reverse the board, >>>re-calculate the new hashkey to match the TBs again? Or do I miss something? >>> >>>Many thanks for any help. >>>Pham >> >> >> >>You don't want to _search_ 2 gigabyte files. EGTBs compute an index that takes >>you directly to the game result for that configuration of pieces. No searching >>whatsoever. The opening book is not _nearly_ that efficient. > >Thank very much. I start to understand. > >Some my new questions: >3) Do all TBs created by different authors use the same index scheme? (I mean if >we could use any of them without changing the codes). No... IE Edwards is different from Nalimov, which is different from Thompson, which is different from Moreland, etc. In fact, some store different values in the tables. Thompson stores distance to conversion, most others store distance to mate, for example. Some are compressed and some are not. Some can be decompressed on the fly, some can not. Not much in common other than the basic algorithm for building them and the results they produce. >4) Could someone explain the technique of compressing TBs (how good/fast, what >kind and how different from normal one)? >Many thanks in advance. Pretty similar to normal compression. But if you know you are compressing bytes, particularly when you have lots of "zeroes" (draw scores) then you can compress more efficiently than if you are trying to compress other types of data (say ASCII which has many zero bits).
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